The purpose of this research is to examine the role of proteolipid (hydrophobic protein complexed with acidic phospholipids) in biologic calcification. By applying techniques developed in the study of microbial calcification to vertebrate systems, the proteolipid dependency of vertebrate calcification will be established. To resolve the dilemma that although proteolipids are normal constituents of biologic membranes, not all tissues calcify, the following approach is proposed. Calcifiability of proteolipid from calcifying tissues, tissues with a potential for ectopic calcification, ectopic deposits and tissues not known to calcify will be determined. How proteolipids capable of nucleating biologic apatite formation differ from those which are non-calcifiable will be examined by comparative characterization. The interaction of proteolipid with other tissue components during mineralization will be evaluated by studies on progressive calcification of cartilage and experimental rickets.